1. Field of the Invention
The invention relates to a switching apparatus comprising an emergency push-button returned to a neutral position by a return spring and concentric with a tubular body receiving an internal sliding part which is retained by a resilient latch in the inactive position before the push-button is struck and is held in an active position by this same latch when this push-button has travelled over a given distance when it is struck, said sliding part being abruptly propelled towards an electric switch by means of a loaded spring placed between it and the push-button.
2. Description of the Prior Art
In such a switch which is known for example from the French Patent Application No. 82 02355, filed on 12th February 1982 for "Emergency stopping device" in the name of the Applicant, the resilient latch and the locking means are in the form of resilient fingers with ramps adapted for cooperating with slanting projections on the body.
In this known switch, the separation of the roles played by the latches before tripping and by the locking means after such tripping results from a desire to control the use of the apparatus such that even actuation of the push-button over a distance not having been able to cause actuation of the switch must be made visible by a particular position of this push-button.
The degree of such protection may in some cases be considered as exaggerated to the extent that an accidental and limited pressure exerted on the push-button cannot be totally excluded, and may even pass unnoticed since, in this case, the switch has not been actuated.
To obtain such quality of protection further requires the use of numerous parts and in particular two concentric sliding parts which it is difficult to house in the body of the push-buttons where the maximum diameter of these latter does not exceed 30 mm or so.
The invention proposes then providing a safety switching device in which the number of moving parts is considerably reduced so as to be able to be housed in a body of small diameter, while continuing to benefit from fraud-proof properties making it practically impossible to actuate the switch as long as the push-button has not reached a position in which its rearward return is impossible; furthermore, this apparatus must have faultless operation relative to forced actuation of the switch if a resilient element placed in the kinematic chain happened to break at the moment when the result of an emergency actuation must be guaranteed.